The molecular basis for the proposed cariogenic properties of Actinomyces viscosus will be investigated in this proposal. The specific attachment of the organism to cemental surfaces will be examined utilizing in vitro assay systems. The role of levans, extracellular slime or other macromolecules in the specific adherence mechanisms will be examined primarily by utilizing mutants of A. viscosus defective in synthesizing individual polysaccharide molecules. This approach will also be used to determine the role of these polysaccharides in the specific interaction of A. viscosus with gram-negative anaerobic bacteria. The glucan-binding protein of rodent strains of A. viscosus will be characterized following purification. The role of plasmids in glucan binding will be assessed by determining the presence or absence of these elements in spontaneous or induced non-glucan binding variants. The regulation of fructosyltransferase production in A. viscosus will also be examined and the role of membranes in the secretion of this and other extracellular enzymes will be investigated.